The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine appropriately mixes air and fuel and generates driving power by burning the mixed gas.
In order to obtain desired output power and combustion efficiency, sufficient air should be supplied to the engine. For this, a turbocharger is used to increase combustion efficiency and supply sufficient air to the engine.
Generally, a turbine of the turbocharger is rotated by pressure of exhaust gas exhausted from the engine, a compressor of the turbocharger compresses fresh air flowing in from the outside, and the compressed air is supplied to a combustion chamber of the engine. The turbocharger has been applied to almost diesel engines, and has recently been applied to gasoline engines.
Further, NOx (nitrous oxide) included in the exhaust gas is regulated as a major air pollutant and many researches have been carried out in order to reduce the amount of NOx in exhaust gases.
An exhaust gas recirculation (EGR) system mounted in a vehicle reduces noxious exhaust gases of the vehicle. Generally, the amount of NOx in the exhaust gas is increased in an oxygen rich air mixture, and the air mixture is combusted well. Therefore, the exhaust gas recirculation system reduces the amount of NOx in the exhaust gas as a consequence of a part of the exhaust gas being recirculated to the air mixture in order to reduce the oxygen ratio in the air mixture and so hinder combustion.
An LP-EGR (low pressure EGR) system is one of the exhaust gas recirculation (EGR) systems. The LP-EGR system recirculates the exhaust gas passing through the turbine of the turbocharger to an intake path of an upstream side of the compressor.
However, the exhaust gas recirculated by the EGR system has high temperature and humidity. Therefore, condensate water is generated when the recirculated exhaust gas and the external air having a low temperature are mixed. We have found that the condensate water has very high acidity by various material included in exhaust gas.
If the condensate water is bumped to a compressor wheel being rotated at a high speed, then the compressor wheel is damaged. According to the conventional art, a method that coats the compressor wheel has been used in order to reduce or prevent damage and corrosion of the compressor wheel, but we have discovered that manufacturing cost is increased for coating the compressor wheel.
Further, various parts (i.e., compressor wheel, or compressor housing, and so on) are corroded by the condensate water having high acidity. And if the condensate water flows into a cylinder of an engine, combustion of the engine becomes unstable.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it does not form the prior art.